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m68k: minor optimizations to g_proc_exit() - use LEA for stackpointer math which is better than ADDing large constants, also only modify the SP reg once

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git-svn-id: trunk@27817 -
This commit is contained in:
Károly Balogh 2014-05-25 01:34:00 +00:00
parent 02dff17ae0
commit 28323135f8
1 changed files with 12 additions and 5 deletions
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17
compiler/m68k/cgcpu.pas
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@ -1716,9 +1716,8 @@ unit cgcpu;
procedure tcg68k.g_proc_exit(list : TAsmList; parasize: longint; nostackframe: boolean);
var
r,hregister : TRegister;
spr : TRegister;
fpr : TRegister;
ref : TReference;
ref2: TReference;
begin
if not nostackframe then
begin
@ -1752,15 +1751,23 @@ unit cgcpu;
hregister:=NR_A0;
cg.a_reg_alloc(list,hregister);
reference_reset_base(ref,NR_STACK_POINTER_REG,0,4);
ref.direction:=dir_inc;
list.concat(taicpu.op_ref_reg(A_MOVE,S_L,ref,hregister));
{ instead of using a postincrement above (which also writes the }
{ stackpointer reg) simply add 4 to the parasize, the instructions }
{ below then take that size into account as well, so SP reg is only }
{ written once (KB) }
parasize:=parasize+4;
r:=NR_SP;
{ can we do a quick addition ... }
if (parasize > 0) and (parasize < 9) then
if (parasize < 9) then
list.concat(taicpu.op_const_reg(A_ADDQ,S_L,parasize,r))
else { nope ... }
list.concat(taicpu.op_const_reg(A_ADD,S_L,parasize,r));
begin
reference_reset_base(ref2,NR_STACK_POINTER_REG,parasize,4);
list.concat(taicpu.op_ref_reg(A_LEA,S_NO,ref2,r));
end;
reference_reset_base(ref,hregister,0,4);
list.concat(taicpu.op_ref(A_JMP,S_NO,ref));